Safe nondeterminism in a deterministic-by-default parallel language

A number of deterministic parallel programming models with strong safety guarantees are emerging, but similar support for nondeterministic algorithms, such as branch and bound search, remains an open question. We present a language together with a type and effect system that supports nondeterministic computations with a deterministic-by-default guarantee: nondeterminism must be explicitly requested via special parallel constructs (marked nd), and any deterministic construct that does not execute any nd construct has deterministic input-output behavior. Moreover, deterministic parallel constructs are always equivalent to a sequential composition of their constituent tasks, even if they enclose, or are enclosed by, nd constructs. Finally, in the execution of nd constructs, interference may occur only between pairs of accesses guarded by atomic statements, so there are no data races, either between atomic statements and unguarded accesses (strong isolation) or between pairs of unguarded ...

• Type: Journal
• Year: 2011
• Where: POPL
• Authors: Robert L. Bocchino Jr., Stephen Heumann, Nima Honarmand, Sarita V. Adve, Vikram S. Adve, Adam Welc, Tatiana Shpeisman
• Keywords: Dynamic Semantics, Parallel Programming Models, POPL 2011, Programming Languages, Static Semantics